Cooling device

ABSTRACT

A cooling device includes a case including a mount surface having a power transistor mounted thereon, a coolant accommodating chamber formed in the case located above the mount surface, for accommodating a coolant capable of evaporating by heat from the power transistor, a cooling pipe provided in the case and being capable of cooling the coolant in a gaseous state, and a defining member provided in the coolant accommodating chamber and being capable of defining in the coolant accommodating chamber a first region capable of guiding the coolant in a gaseous state evaporated by the heat from the power transistor toward the cooling pipe, and a second region located downstream in a flow direction of the coolant with respect to the first region and being capable of guiding the coolant cooled by the cooling pipe toward a bottom of the coolant accommodating chamber.

TECHNICAL FIELD

The present invention relates to a cooling device, and more particularly to a cooling device for cooling an object to be cooled by using heat of vaporization of a coolant stored in the cooling device.

BACKGROUND ART

Various kinds of cooling devices for cooling an object to be cooled such as electronic equipment have been conventionally proposed (Japanese Patent Laying-Open No. 2005-11983). For example, a cooling device for an electronic circuit described in Japanese Patent Laying-Open No. 2004-349307 includes a plurality of cooling units. This cooling unit is constituted of a cooling part and a connection part. A coolant injection hole is formed in the cooling part, and a coolant is injected into this coolant injection hole. The connection part in contact with cooling water is provided on a surface of an upper portion of the above cooling part. This cooling device, which has an element adhered to a surface of the cooling part, cools the element by the coolant, and cools the coolant by the cooling liquid.

In this cooling device, part of the coolant evaporates by heat from the element. Then, the gaseous coolant moves upward inside the coolant injection hole, is cooled by the cooling liquid and condensed, and returns to a bottom of the coolant injection hole again.

In the above cooling device described in Japanese Patent Laying-Open No. 2004-349307, the gaseous coolant and the coolant still in a gaseous state but having been cooled by the cooling liquid are mixed inside the coolant injection hole.

Thus, a flow of the gaseous coolant is not smooth inside the coolant injection hole, making it difficult for the coolant evaporated by the heat from the element to move upward inside the coolant injection hole and to be cooled by the cooling water. Accordingly, there has been a problem of difficulty in dissipating the heat from the element into the cooling water, resulting in lower efficiency of cooling the element.

DISCLOSURE OF THE INVENTION

The present invention was made in view of the above-described problems, and an object thereof is to provide a cooling device with improved efficiency of cooling an object to be cooled such as an element by ensuring a flow and circulation of a gaseous coolant evaporated by heat from the object to be cooled.

A cooling device according to the present invention includes a case including a mount part having an object to be cooled mounted thereon, and a coolant accommodating chamber formed in the case located above the mount part, for accommodating a coolant capable of evaporating by heat from the object to be cooled. In addition, this cooling device includes a cooling part provided in the case and being capable of cooling the coolant in a gaseous state, and a defining member provided in the coolant accommodating chamber and being capable of defining in the coolant accommodating chamber a first region capable of guiding the coolant in a gaseous state evaporated by the heat from the object to be cooled toward the cooling part, and a second region located downstream in a flow direction of the coolant with respect to the first region and being capable of guiding the coolant cooled by the cooling part toward a bottom of the coolant accommodating chamber.

Preferably, the above defining member includes a wall portion extending from a side of the bottom of the coolant accommodating chamber to reach a central portion in a height direction of the coolant accommodating chamber, and a swelling portion provided on an upper end portion of the wall portion and having a curved surface.

Preferably, an inner surface of the case defining the above coolant accommodating chamber includes the bottom projecting toward the object to be cooled. Preferably, a plurality of the above defining members are provided at a distance from one another.

Preferably, the above defining member is provided in a position at a distance in a width direction of the object to be cooled from a central portion in the width direction of the object to be cooled.

Preferably, the bottom of the above coolant accommodating chamber is partitioned by the defining member into a first storage part located upstream in the flow direction of the coolant in a gaseous state in the first region, for storing the coolant that evaporates by the heat from the object to be cooled, and a second storage part located downstream in the flow direction of the coolant in a gaseous state in the second region, for storing the coolant condensed by the cooling part. In addition, the above defining member includes a flow portion capable of guiding the coolant in the second storage part to the first storage part.

Preferably, the above cooling part includes a cooling fin provided in the coolant accommodating chamber. Preferably, the above cooling part includes a cooling pipe through which a cooling medium capable of cooling heat from the cooling fin flows, and the cooling pipe includes a branch portion reaching inside the cooling fin.

It is intended as of filing to combine all features described above as appropriate.

According to the cooling device of the present invention, the coolant evaporated by the heat from the object to be cooled is guided toward the cooling part through the first region, and then the coolant cooled by the cooling part is guided to the bottom of the coolant accommodating chamber through the second region, thereby attaining good coolant circulation to improve efficiency of cooling the object to be cooled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating a configuration of a main part of a PCU.

FIG. 2 is an exploded perspective view of a cooling device including cooling cells for cooling power transistors.

FIG. 3 is a perspective view illustrating in detail an internal structure of the cooling cell in the cooling device.

FIG. 4 is a cross-sectional view of the cooling cell.

FIG. 5 is a cross-sectional view illustrating a modification of cooling fins and a cooling pipe.

FIG. 6 is a modification employing air-cooling fins instead of the cooling pipe through which a coolant flows.

FIG. 7 is a cross-sectional view illustrating a first modification of the cooling cell.

FIG. 8 is a cross-sectional view illustrating a second modification of the cooling cell.

BEST MODES FOR CARRYING OUT THE INVENTION

A cooling device 10 according to the present embodiment will be described with reference to FIGS. 1 to 8. It is noted that the same or corresponding elements have the same reference characters, so that description thereof may not be repeated. If any reference to a number, an amount and the like is made in embodiments described below, the scope of the present invention is not necessarily limited to that number, amount and the like unless otherwise specified. Further, in the following embodiments, each constituent element is not necessarily essential to the present invention unless otherwise specified. Furthermore, if there are a plurality of embodiments below, it is originally intended to combine features of the respective embodiments as appropriate unless otherwise specified.

FIG. 1 is a circuit diagram illustrating a configuration of a main part of a PCU 700. Referring to FIG. 1, PCU 700 includes a converter 710, an inverter 720, a control device 730, capacitors C1, C2, power supply lines PL1 to PL3, and output lines 740U, 740V, 740W. Converter 710 is connected between a battery 800 and inverter 720, and inverter 720 is connected to a motor generator 100 via output lines 740U, 740V, 740W.

Battery 800 connected to converter 710 is a secondary battery such as a nickel metal hydride battery, a lithium-ion battery or the like. Battery 800 supplies a generated direct-current voltage to converter 710, and is charged with a DC voltage received from converter 710.

Converter 710 includes power transistors Q1, Q2, diodes D1, D2, and a reactor L. Power transistors Q1, Q2 are connected in series between power supply lines PL2 and PL3, and receive a control signal from control device 730 at their bases. Diodes D1, D2 are connected between collectors and emitters of power transistors Q1, Q2, respectively, to allow a current flow from an emitter side to a collector side of power transistors Q1, Q2, respectively. Reactor L has one end connected to power supply line PL1 connected to a positive electrode of battery 800, and the other end connected to a node between power transistors Q1 and Q2.

This converter 710 boosts the DC voltage received from battery 800 by using reactor L, and supplies the boosted voltage to power supply line L2. Converter 710 also down-converts a DC voltage received from inverter 720 and charges battery 800. Inverter 720 includes a U-phase arm 750U, a V-phase arm 750V and a W-phase arm 750W. Arms of the respective phases are connected in parallel between power supply lines PL2 and PL3. U-phase arm 750U includes power transistors Q3, Q4 connected in series, V-phase arm 750V includes power transistors Q5, Q6 connected in series, and W-phase arm 750W includes power transistors Q7, Q8 connected in series. Diodes D3 to D8 are connected between collectors and emitters of power transistors Q3 to Q8, respectively, to allow a current flow from an emitter side to a collector side of power transistors Q3 to Q8, respectively. In addition, nodes between the respective power transistors in the arms of the respective phases are connected to sides opposite to neutral points of the coils of the respective phases of motor generator 100 via output lines 740U, 740V, 740W, respectively.

In response to a control signal from control device 730, this inverter 720 converts the DC voltage received from power supply line PL2 to an alternating-current voltage and outputs the resultant voltage to motor generator 100. Inverter 720 also rectifies an AC voltage generated by motor generator 100 to a DC voltage and supplies the resultant voltage to power supply line PL2.

Capacitor C1 is connected between power supply lines PL1 and PL3, and smoothes a voltage level of power supply line PL1. Additionally, capacitor C2 is connected between power supply lines PL2 and PL3, and smoothes a voltage level of power supply line PL2.

Control device 730 calculates a voltage of a coil of each phase of motor generator 100 based on a rotating angle of a rotor in motor generator 100, a motor torque control value, a current value of each phase of motor generator 100, and an input voltage of inverter 720, and based on a result of that calculation, generates a PWM (Pulse Width Modulation) signal for turning power transistors Q3 to Q8 on/off and outputs the signal to inverter 720.

Further, control device 730 calculates a duty ratio of power transistors Q1, Q2 for optimizing the input voltage of inverter 720 based on the above-mentioned motor torque control value and a motor speed, and based on a result of that calculation, generates a PWM signal for turning power transistors Q1, Q2 on/off and outputs the signal to converter 710.

Furthermore, control device 730 controls switching operation of power transistors Q1 to Q8 in converter 710 and inverter 720, in order to convert AC power generated by motor generator 100 to DC power and charge battery 800.

In this PCU 700, in response to a control signal from control device 730, converter 710 boosts a DC voltage received from battery 800 and supplies the resultant voltage to power supply line PL2. Then, inverter 720 receives from power supply line PL2 the DC voltage smoothed by capacitor C2, converts the received DC voltage to an AC voltage and outputs the resultant voltage to motor generator 100.

Moreover, inverter 720 converts an AC voltage generated by regenerative operation of motor generator 100 to a DC voltage, and outputs the resultant voltage to power supply line PL2. Then, converter 710 receives from power supply line PL2 the DC voltage smoothed by capacitor C2, down-converts the received DC voltage and charges battery 800.

FIG. 2 is an exploded perspective view of cooling device 10 including cooling cells for cooling power transistors Q1 to Q8. FIG. 3 is a perspective view illustrating in detail an internal structure of a cooling cell 15 in cooling device 10. FIG. 4 is a cross-sectional view of cooling cell 15.

As shown in FIG. 2, cooling device 10 includes a case 16, and a plurality of cooling cells 15 for cooling respective power transistors Q1 to Q8.

Case 16 includes a mount member 11 having a mount surface 11 a on which the plurality of power transistors (objects to be cooled) Q (Q1 to Q8) are mounted, a housing 12 in which the plurality of cooling cells 15 are defined after mount member 11 is mounted on housing 12, and a cooling housing 14 having a cooling pipe 13 disposed therein through which a cooling medium A flows. It is noted that mount member 11, housing 12 and cooling housing 14 are all made of a metal having a high thermal conductivity, e.g., copper, aluminum or the like.

Mount surface 11 a of mount member 11 is formed as a flat surface, and an insulating film 11 b is formed as a plate on this mount surface 11 a. A circuit board 11 c having a circuit pattern formed thereon is formed on an upper surface of this insulating film 11 b. The plurality of power transistors Q (Q1 to Q8) are mounted on a main surface of this circuit board 11 c. It is noted that not-shown solder or the like is formed between insulating film 11 b and mount surface 11 a, to fix insulating film 11 b on mount surface 11 a. When mount member 11 is mounted on housing 12, cooling cells 15 corresponding to respective power transistors Q (Q1 to Q8) are defined. As such, respective power transistors Q (Q1 to Q8) are cooled separately and independently by respective cooling cells 15.

A plurality of recesses 20 b having an inner surface in a semi-elliptical cylindrical form are formed in housing 12. As shown in FIGS. 3 and 4, a plurality of recesses 20 c in a semi-elliptical cylindrical form are formed in mount member 11 as well. When mount member 11 is mounted on housing 12, an inner surface of housing 12 defining recesses 20 b and an inner surface of mount member 11 defining recesses 20 c form a coolant accommodating chamber 20 a capable of sealing a coolant W.

Here, the inner surface of mount member 11 defining coolant accommodating chamber 20 a is curved to project toward power transistor Q (Q1 to Q8). In cooling device 10 according to the present embodiment, the inner surface of mount member 11 defining coolant accommodating chamber 20 a has an elliptical shape. In addition, a portion having the largest radius of curvature of a circumference of the elliptical shape is located at a bottom 20 d.

Thus, a portion of the inner surface of case 16 defining coolant accommodating chamber 20 a, which is located at bottom 20 d, is closest to mount surface 11 a, and mount surface 11 a has power transistor Q (Q1 to Q8) provided in a position facing bottom 20 d.

A thickness t of case 16 located between coolant accommodating chamber 20 a and mount surface 11 a has smallest thickness t1 at a portion located between bottom 20 d and mount surface 11 a. On the other hand, the thickness of the portion located between coolant accommodating chamber 20 a and mount surface 11 a increases as distance from bottom 20 d increases.

That is, the inner surface of case 16 defining coolant accommodating chamber 20 a is such that a distance between the inner surface of case 16 defining coolant accommodating chamber 20 a and mount surface 11 a increases as distance from bottom 20 d increases.

This coolant accommodating chamber 20 a is filled with coolant W such as water, an insulative coolant, alcohol having a lower evaporation temperature than water, or the like. Coolant W is accumulated in bottom 20 d. In this manner, coolant W is located in a portion closest to power transistor Q (Q1 to Q8) in coolant accommodating chamber 20 a.

Here, as shown in FIG. 3, coolant accommodating chamber 20 a extends in one direction along mount surface 11 a. Additionally, in coolant accommodating chamber 20 a, two (a plurality of) defining members 32A, 32B are provided which extend in the direction in which this coolant accommodating chamber 20 a extends.

Defining members 32A, 32B extend in the direction in which coolant accommodating chamber 20 a extends, and are provided at a distance from each other in a width direction orthogonal to the direction in which coolant accommodating chamber 20 a extends.

A distance between defining members 32A and 32B is equal to a width of power transistor Q (Q1 to Q8) or slightly greater than that, and bottom 20 d is located between these defining members 32A and 32B.

Here, in FIG. 4, a portion of case 16, which is located between a portion located between defining members 32A and 32B and power transistor Q (Q1 to Q8), is a thin portion 26. In addition, a portion located in the width direction of coolant accommodating chamber 20 a with respect to thin portion 26 is a thick portion 25 which is greater in thickness than thin portion 26.

These defining members 32A, 32B partition coolant accommodating chamber 20 a into a region (first region) K1 above power transistor Q (Q1 to Q8), which is defined between defining members 32A and 32B and extends upward, and a region (second region) K2 which is a portion other than region K1 and defined by defining members 32A, 32B and the inner surface of coolant accommodating chamber 20 a.

These defining members 32A, 32B include wall portions 31A, 31B standing from the bottom of coolant accommodating chamber 20 a to reach a central portion in a height direction thereof, and swelling portions 30A, 30B formed on upper end portions of these wall portions 31A, 31B, respectively.

Region K1 is defined between defining members 32A and 32B, and region K2 is defined as regions between respective surfaces of swelling portions 30A, 30B and the inner surface defining coolant accommodating chamber 20 a, and between side surfaces of wall portions 31A, 31B and coolant accommodating chamber 20 a.

Swelling portions 30A, 30B extend in the direction in which coolant accommodating chamber 20 a extends, and have a smoothly curved surface, the surfaces of swelling portions 30A, 30B extending along the inner surface of coolant accommodating chamber 20 a. It is noted that, in cooling device 10 according to the present embodiment, swelling portions 30A, 30B have a substantially cylindrical shape.

Here, swelling portion 30A is formed to project not toward a side surface of wall portion 31A facing wall portion 31B but toward a side surface located opposite to this side surface.

Swelling portion 30B is also formed to project not toward a side surface of wall portion 31B facing wall portion 31A but toward a side surface located opposite to this side surface.

Accordingly, the side surface in the surface of defining member 32A, which faces defining member 32B, is substantially flat, and the side surface in the surface of defining member 32B, which faces defining member 32A, is substantially flat. As such, an inner surface of region K1 located between defining members 32A and 32B is substantially flat.

Here, lower ends of defining members 32A, 32B are provided slightly distant from the bottom surface of coolant accommodating chamber 20 a, with a clearance (opening) GP being formed between the lower ends of defining members 32A, 32B and the inner surface of coolant accommodating chamber 20 a.

Therefore, coolant W can flow back and forth through a portion located between defining members 32A and 32B, a portion located between defining member 32A and the inner surface of coolant accommodating chamber 20 a, and a portion located between defining member 32B and the inner surface of coolant accommodating chamber 20 a, on the side of a bottom surface of coolant accommodating chamber 20 a.

In FIGS. 2 and 3, on upper end portions of defining members 32A, 32B, a plurality of cooling fins 21 are arranged at a distance from one another in the direction in which defining members 32A, 32B extend.

Here, cooling housing 14 is provided on an upper surface of housing 12, and cooling pipe 13 through which cooling medium A such as water flows is disposed in this cooling housing 14. This cooling pipe 13 extends in the direction in which cooling fins 21 are arranged.

Cooling operation of cooling power transistors Q (Q1 to Q8) by cooling device 10 structured as above will be described.

In FIGS. 3 and 4, when a temperature of power transistor Q (Q1 to Q8) increases, heat from power transistor Q (Q1 to Q8) is transmitted to coolant W via thin portion 26. Here, bottom 20 d is located in a portion closest to power transistor Q (Q1 to Q8) in coolant accommodating chamber 20 a. This bottom 20 d is located between defining members 32A and 32B, so that evaporated coolant W in a gaseous state goes through region K1 and moves upward. Here, the surfaces of defining members 32A, 32B defining region K1 are substantially flat as described above, so that evaporated coolant W in a gaseous state is guided to space among cooling fins 21. Upon reaching the space among cooling fins 21, coolant W is cooled by dissipating heat into cooling fins 21. The heat dissipated into cooling fins 21 is dissipated into cooling medium A flowing through cooling pipe 13. It is noted that cooling pipe 13 is connected to a heat exchanger (radiator) or the like for exchanging heat between outside air from outside and cooling medium A, and cooling medium A is cooled by outside air.

FIG. 5 is a cross-sectional view illustrating a modification of cooling fins 21 and cooling pipe 13. In this example shown in FIG. 5, cooling pipe 13 includes a branch pipe (branch portion) 13 a branched from cooling pipe 13 and entering cooling fins 21. In this example shown in FIG. 5, coolant W flows into branch pipe 13 a, so that cooling fins 21 can be cooled by coolant W to thereby improve cooling capability of cooling fins 21.

FIG. 6 is a modification employing air-cooling fins instead of cooling pipe 13 through which coolant W flows. In this example shown in FIG. 6, a plurality of air-cooling fins 23 extending in the direction in which defining members 32A, 32B extend are provided on the upper surface of housing 12. Outside air taken from outside is supplied to these air-cooling fins 23 and heat from cooling fins 21 is dissipated into the same.

In FIGS. 3 and 4, gaseous coolant W coming out from between swelling portions 30A and 30B of defining members 32A, 32B enters region K2 while spreading around. Here, with the inner surface of case 16 defining coolant accommodating chamber 20 a and the surfaces of swelling portions 30A, 30B all having a curved surface, gaseous coolant W flows without stagnation.

Then, gaseous coolant W is cooled by cooling fins 21 while flowing to wrap around respective swelling portions 30A, 30B.

Since gaseous coolant W flows to go around swelling portions 30A, 30B in this manner, a length of a path where gaseous coolant W is in contact with cooling fins 21 is increased, to cool gaseous coolant W. That is, evaporated coolant W in a gaseous state is supplied from a central portion of cooling fins 21 to the space among cooling fins 21, and flows toward opposing end portions of cooling fins 21. Gaseous coolant W is defined by defining members 32A, 32B to then go through portions on the sides of the opposing end portions of cooling fins 21 and flow toward bottom 20 d.

Then, gaseous coolant W is reduced in volume in the course of being cooled by cooling fins 21, and then condenses into a liquid.

Therefore, by the time when gaseous coolant W emitted from region K1 reaches space between wall portions 31A, 31B of defining members 32A, 32B and case 16 defining the inner surface of coolant accommodating chamber 20 a, gaseous coolant W has been reduced in volume or has already condensed into a liquid.

A pressure is lowered in region K2 due to the reduction in volume and the condensation into a liquid of gaseous coolant W as described above, causing gaseous coolant W in region K1 to be drawn into region K2. As a result, circulation of coolant W is facilitated, thereby cooling power transistor Q (Q1 to Q8) well.

Here, a portion of the inner surface of case 16 defining coolant accommodating chamber 20 a, which is located below lower ends of cooling fins 21, is curved such that it comes closer to bottom 20 d as it goes downward. Because of this, condensed coolant W in a liquid state flows along the inner surface of coolant accommodating chamber 20 a and reaches bottom 20 d. In particular, the inner surface of coolant accommodating chamber 20 a defining vicinity of bottom 20 d is formed as a curved surface having a large radius of curvature, and condensed coolant W flows downward along the inner surface of coolant accommodating chamber 20 a. Accordingly, dripping of the condensed coolant is suppressed.

Then, liquid coolant W returned to the region located between defining member 32A and the inner surface of coolant accommodating chamber 20 a or to the portion located between defining member 32B and the inner surface of coolant accommodating chamber 20 a on the side of the bottom surface of coolant accommodating chamber 20 a passes the lower ends of defining members 32A, 32B to enter the portion located between defining members 32A and 32B, and then evaporates again.

When the heat from power transistor Q (Q1 to Q8) is transmitted to case 16, the heat is transmitted from thin portion 26 not only to coolant W located between defining members 32A and 32B, but also to thick portion 25. Then, the heat is transmitted from this thick portion 25 to coolant W. In particular, as thick portion 25 is greater in thickness than thin portion 26, the heat is transmitted well from thin portion 26 to thick portion 25. Here, a liquid level of coolant W reaches a level above thick portion 25, and the heat transmitted to thick portion 25 can also be dissipated into coolant W. That is, with a large area of heat transmission from case 16 to coolant W, the heat from power transistor Q (Q1 to Q8) can be dissipated into coolant W well.

Here, in cooling device 10 according to the present embodiment, cooling cells 15 corresponding to respective power transistors Q (Q1 to Q8) are provided. Accordingly, if a temperature of any of power transistors Q (Q1 to Q8) increases, coolant W in cooling cell 15 corresponding to this power transistor Q (Q1 to Q8) evaporates, thereby actively cooling that power transistor Q (Q1 to Q8). It is noted that cooling cells 15 may extend in a direction in which power transistors Q (Q1 to Q8) are arranged, to cool the plurality of transistors Q (Q1 to Q8) collectively.

FIG. 7 is a cross-sectional view illustrating a first modification of cooling cell 15. In this example shown in FIG. 7, a defining member 44 includes a wall portion 41 extending from the side of bottom 20 d of coolant accommodating chamber 20 a to reach the central portion in the height direction of coolant accommodating chamber 20 a, and a swelling portion 40 formed on an upper end portion of this wall portion 41.

Wall portion 41 stands upright from the side of bottom 20 d of coolant accommodating chamber 20 a to reach the central portion of coolant accommodating chamber 20 a. This wall portion 41 is provided in a position displaced in a width direction of power transistor Q (Q1 to Q8). An outer surface of swelling portion 40 is formed as a smoothly curved surface. Particularly in this example shown in FIG. 7, swelling portion 40 has a substantially elliptical shape, which is a shape substantially similar to the inner surface of coolant accommodating chamber 20 a and is a shape as the inner surface of coolant accommodating chamber 20 a reduced in size.

In addition, swelling portion 40 projects to overhang power transistor Q (Q1 to Q8) from the upper end portion of wall portion 41.

Accordingly, the inside of coolant accommodating chamber 20 a is partitioned into a region K1 defined by wall portion 41, the surface of swelling portion 40 located above bottom 20 d and part of the inner surface of coolant accommodating chamber 20 a, and located below cooling fins 21, and a region K2 located downstream in a flow direction (direction indicated by an arrow in the figure) R of gaseous coolant W with respect to this region K1.

In this example shown in FIG. 7, coolant W located at bottom 20 d evaporates by the heat from power transistor Q (Q1 to Q8). Then, evaporated coolant W in a gaseous state moves upward, and flows along swelling portion 40 or the inner surface of coolant accommodating chamber 20 a. Here, the surface of swelling portion 40 and the inner surface of coolant accommodating chamber 20 a are curved, and slowing of the flow of gaseous coolant W is suppressed.

In particular, since swelling portion 40 has a curved surface, a path of gaseous coolant W is also curved along the surface of swelling portion 40 to increase a length of a path of contact with cooling fins 21. This leads to an increase in area where gaseous coolant W and cooling fins 21 are in contact with one another, so that coolant W is cooled well.

That is, in this example shown in FIG. 7, coolant W flows from the side of one end portion of cooling fins 21 toward the side of the other end portion, thereby ensuring an area of contact between coolant W and cooling fins 21.

Further, gaseous coolant W that has reached the space among cooling fins 21 and entered region K2 is cooled by cooling fins 21 while flowing in flow direction R. Gaseous coolant W that has been cooled is reduced in volume and condenses into a liquid, causing a reduction of pressure in downstream region K2. As a result, gaseous coolant W located in region K1 is drawn into region K2.

In this manner, circulation of gaseous coolant. W is facilitated, thus ensuring efficiency of cooling the heat from power transistor Q (Q1 to Q8).

FIG. 8 is a cross-sectional view illustrating a second modification of cooling cell 15. In this example shown in FIG. 8, a portion of mount member 11 located between coolant accommodating chamber 20 a and mount surface 11 a has a substantially uniform thickness. That is, bottom 20 d of coolant accommodating chamber 20 a is formed as a flat surface. In addition, a defining member 45 is provided in a position distant from power transistor Q (Q1 to Q8). This defining member 45 also includes a wall portion 43 and a swelling portion 42, and defines region K1 and region K2 inside coolant accommodating chamber 20 a.

Here, power transistor Q (Q1 to Q8) is mounted on mount surface 11 a located opposite to a portion of bottom 20 d at which region K1 is located.

Therefore, coolant W located in region K1 evaporates, and this evaporated coolant W in a gaseous state is guided toward cooling fins 21, enters region K2, and is then cooled by cooling fins 21 and condenses. In this manner, again in this cooling device shown in FIG. 8, circulation of coolant W can be ensured, thereby cooling power transistor Q (Q1 to Q8) well.

While the embodiments of the present invention have been described as above, it should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

INDUSTRIAL APPLICABILITY

The present invention relates to a cooling device, and it is particularly suitable for a cooling device for cooling an object to be cooled by using heat of vaporization of a coolant stored in the cooling device. 

1. A cooling device comprising: a case including a mount part having an object to be cooled mounted thereon; a coolant accommodating chamber formed in said case located above said mount part, for accommodating a coolant capable of evaporating by heat from said object to be cooled; a cooling part provided in said case and being capable of cooling said coolant in a gaseous state; and a defining member provided in said coolant accommodating chamber and being capable of defining in said coolant accommodating chamber a first region capable of guiding said coolant in a gaseous state evaporated by the heat from said object to be cooled toward said cooling part, and a second region located downstream in a flow direction of said coolant with respect to said first region and being capable of guiding said coolant cooled by said cooling part toward a bottom of said coolant accommodating chamber, said defining member including a wall portion extending from a side of the bottom of said coolant accommodating chamber to reach a central portion in a height direction of said coolant accommodating chamber, and a swelling portion provided on an upper end portion of said wall portion and having a curved surface.
 2. (canceled)
 3. The cooling device according to claim 1, wherein an inner surface of said case defining said coolant accommodating chamber includes the bottom projecting toward said object to be cooled, and is formed such that a distance between the inner surface of said case defining said coolant accommodating chamber and said mount part is reduced toward said bottom.
 4. The cooling device according to claim 1, wherein a plurality of said defining members are provided at a distance from one another.
 5. The cooling device according to claim 1, wherein said defining member is provided in a position at a distance in a width direction of said object to be cooled from a central portion in the width direction of said object to be cooled.
 6. The cooling device according to claim 1, wherein the bottom of said coolant accommodating chamber is partitioned by said defining member into a first storage part located upstream in the flow direction of said coolant in a gaseous state in said first region, for storing said coolant that evaporates by the heat from said object to be cooled, and a second storage part located downstream in the flow direction of said coolant in a gaseous state in said second region, for storing said coolant in a liquid state condensed by said cooling part, and said defining member includes a flow portion capable of guiding said coolant in said second storage part to said first storage part.
 7. The cooling device according to claim 1, wherein said cooling part includes a cooling fin provided in said coolant accommodating chamber, said cooling fin being provided on an upper end portion of said defining member, and said coolant is cooled by said cooling fin while flowing in said flow direction, and flows toward inside of said second region.
 8. The cooling device according to claim 7, wherein said cooling part includes a cooling pipe through which a cooling medium capable of cooling heat from said cooling fin flows, and said cooling pipe includes a branch portion reaching inside said cooling fin. 